mfd: arizona: Make some symbols static

The sparse tool complains as follows:

drivers/mfd/arizona-spi.c:28:31: warning:
 symbol 'reset_gpios' was not declared. Should it be static?
drivers/mfd/arizona-spi.c:29:31: warning:
 symbol 'ldoena_gpios' was not declared. Should it be static?

Those symbols are not used outside of arizona-spi.c, so this
commit marks them static.

Fixes: e9338367 ("mfd: arizona: Add support for ACPI enumeration of WM5102 connected over SPI")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>